[julia-users] 100X boost in BigInt addition when using in-place functionality

[Ariel Keselman]

I'm working on a PR based on this benchmark, see image below, comments 
welcome!

<https://lh6.googleusercontent.com/-oudffKuh7f4/VM9RNAiCXvI/AAAAAAAANOY/e1_1I8ecvbE/s1600/Screenshot%2Bfrom%2B2015-02-02%2B12%3A26%3A27.png>